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Time-resolved measurements of highly-polymerised negative ions in rf silane plasma deposition experiments

Technical Report:

Abstract

The time-resolved fluxes of negative polysilicon hydride ions from a power-modulated rf silane plasma have been measured by quadrupole mass spectrometry and modeled using a simple polymerisation scheme. Experiments were performed with plasma parameters suitable for high-quality amorphous silicon deposition. Polysilicon hydride anions diffuse from the plasma with low energy (approximately 0.5 eV) during the afterglow after the electron density has decayed and the sheath fields have collapsed. The mass-dependence of the temporal behavior of the anion loss flux demonstrates that the plasma composition is influenced by the modulation frequency. The negative species attain much higher masses than the positive or neutral species, and anions containing as many as sixteen silicon atoms have been observed, corresponding to the 500 amu limit of the mass spectrometer. This suggests that negative ions could be the precursors to particle formation. Ion-molecule and ion-ion reactions are discussed and a simple negative ion polymerisation scheme is proposed which qualitatively reproduces the experimental results. The model shows that the densities of high mass negative ions in the plasma are strongly reduced by modulation frequencies near 1 kHz. Each plasma period is then too short for the polymerisation chain to propagate to high masses before the elementary  More>>
Authors:
Howling, A A; Sansonnens, L; Dorier, J L; Hollenstein, C [1] 
  1. Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
Publication Date:
Jul 01, 1993
Product Type:
Technical Report
Report Number:
LRP-479/93
Reference Number:
SCA: 700320; PA: AIX-25:007838; EDB-94:016574; ERA-19:007829; NTS-94:015330; SN: 94001127193
Resource Relation:
Other Information: PBD: Jul 1993
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANIONS; POLYMERIZATION; PLASMA; SILANES; PLASMA DIAGNOSTICS; MASS SPECTROSCOPY; DEPOSITION; ELECTRON DENSITY; EXPERIMENTAL DATA; ION-ION COLLISIONS; ION-MOLECULE COLLISIONS; PLASMA SHEATH; QUADRUPOLES; RF SYSTEMS; THEORETICAL DATA; TIME RESOLUTION; 700320; PLASMA DIAGNOSTIC TECHNIQUES AND INSTRUMENTATION
OSTI ID:
10113862
Research Organizations:
Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
Country of Origin:
Switzerland
Language:
English
Other Identifying Numbers:
Other: ON: DE94611447; TRN: CH9300593007838
Availability:
OSTI; NTIS; INIS
Submitting Site:
CHN
Size:
47 p.
Announcement Date:
Jun 30, 2005

Technical Report:

Citation Formats

Howling, A A, Sansonnens, L, Dorier, J L, and Hollenstein, C. Time-resolved measurements of highly-polymerised negative ions in rf silane plasma deposition experiments. Switzerland: N. p., 1993. Web.
Howling, A A, Sansonnens, L, Dorier, J L, & Hollenstein, C. Time-resolved measurements of highly-polymerised negative ions in rf silane plasma deposition experiments. Switzerland.
Howling, A A, Sansonnens, L, Dorier, J L, and Hollenstein, C. 1993. "Time-resolved measurements of highly-polymerised negative ions in rf silane plasma deposition experiments." Switzerland.
@misc{etde_10113862,
title = {Time-resolved measurements of highly-polymerised negative ions in rf silane plasma deposition experiments}
author = {Howling, A A, Sansonnens, L, Dorier, J L, and Hollenstein, C}
abstractNote = {The time-resolved fluxes of negative polysilicon hydride ions from a power-modulated rf silane plasma have been measured by quadrupole mass spectrometry and modeled using a simple polymerisation scheme. Experiments were performed with plasma parameters suitable for high-quality amorphous silicon deposition. Polysilicon hydride anions diffuse from the plasma with low energy (approximately 0.5 eV) during the afterglow after the electron density has decayed and the sheath fields have collapsed. The mass-dependence of the temporal behavior of the anion loss flux demonstrates that the plasma composition is influenced by the modulation frequency. The negative species attain much higher masses than the positive or neutral species, and anions containing as many as sixteen silicon atoms have been observed, corresponding to the 500 amu limit of the mass spectrometer. This suggests that negative ions could be the precursors to particle formation. Ion-molecule and ion-ion reactions are discussed and a simple negative ion polymerisation scheme is proposed which qualitatively reproduces the experimental results. The model shows that the densities of high mass negative ions in the plasma are strongly reduced by modulation frequencies near 1 kHz. Each plasma period is then too short for the polymerisation chain to propagate to high masses before the elementary anions are lost in each subsequent afterglow period. This explains why modulation of the rf power can reduce particle contamination. We conclude that, for the case of silane rf plasmas, the initiation steps which ultimately lead to particle contamination proceed by negative ion polymerisation. (author) 15 figs., 72 refs.}
place = {Switzerland}
year = {1993}
month = {Jul}
}